Pipelines have been a comparatively safe mode of transportation, with few deaths and injuries while transporting extremely large quantities of energy products across many countries. Nevertheless, they present a substantial threat of low-probability, high consequence accidents. The risk is concentrated geographically. When pipeline incidents occur, most harm to people, property, and the environment is in High Consequence Areas (HCAs) with a significant population, water, or other sensitive natural resources.

Analysis of the Pipeline and Hazardous Materials Safety Administration (PHMSA) liquid pipeline data indicates spill volumes are highly variable year-to-year and the cost of a spill can be highly disproportionate to volumes. For example, high costs in 2010 were based on one high volume spill with disproportionately high per-barrel costs. Overall, the system-level spill incident rate is surprisingly constant at about 0.002 incident/mile/year1.

  • Median spill volume is 2 BBLs
  • 70% of all spills are less than 10 BBLs in size
  • 40% are less than 1 BBL
  • Large spills greater than 1,000 BBLs constitute only about 3% of all spills.
  • Monster spills greater than 10,000 BBLs constitute less than 0.4% of all events.

Based on the current incident rate in the United States (~400 spills/year), we can expect 1 to 2 such large spills every year.

This adds weight and urgency to the need for a solid leak detection program and great spill response plan. The leak detection program itself should integrate with other pipeline operating programs and quantifiable tools to minimize total spill impact, such as:

  • Spill cost model
  • Pipeline design that is robust in the event of leak/spill
  • Inspection program
  • Emergency response plan
  • Spill risk management program

Analysis of the PHMSA data indicates that situational costs may be a larger component of total spill costs than the volume-related costs. Situational costs can depend on elements such as:

  • Discharge into HCA, wetland, river crossing, reservoir, etc.
  • Poorly implemented operator spill response
  • Large number of injured parties
  • Personal injury or death

To minimize the consequence of spillage and situational costs, other tools such as Atmos SIM offline simulation software can be used to:

  • Analyze spill volume based on different response scenarios in different geographical locations along a pipeline to identify high-risk locations where a spill can have the most consequences
  • Test scenarios for the most efficient deployment of hardware such as emergency shutdown valves to minimize the consequence of a leak in different locations
  • Test scenarios for the most effective shutdown procedures to minimize the consequence of a leak due to pressure surges

Even well operated and maintained pipelines are at risk from external threats beyond their control such as third party strikes and weather events. For example, of the top ten liquid/gas transmission pipeline accidents (1986-2012) in terms of economic consequences, four were attributed to high winds or heavy rains/floods2. Faster/better leak detection cannot prevent these events and it reduces only one aspect of spill volumes. Understanding the hydraulics of the pipelines and implementing a design that is robust and effective in minimizing the spill are also important components in mitigating the consequence of leaks. Atmos has developed our offline hydraulic simulation software, Atmos SIM, to meet the need for a fast, accurate and user-friendly tool to quickly conduct these studies.

Using Atmos Surge Analysis, you can optimize operations to minimize stresses that can weaken or even rupture a pipeline. Atmos Trainer is effective in ensuring controllers are aware of how their pipeline control systems will respond in the case of a leak at different locations as these responses can sometimes mask the effects of a leak thus delaying the appropriate response to an alarm.


  1. Henrie M., Carpenter P., Nicholas E. “Spill Risk Management in an API 1175 Context”. API RP 1175 Pipeline Leak Detection-Program Management Workshop. San Antonio, Texas. April 26 - 27 2017.
  2. Secretary of State, Kowaleski R. “Program Evaluation: Pipeline Integrity Management. October 31, 2013.

By: Atmos International
Date: 11 October 2019